A combination of xylanase, amylase and protease influences growth performance, nutrient utilisation, starch and protein digestive dynamics in broiler chickens offered maize-, sorghum- and wheat-based diets

Abstract

In order to examine the influence of an enzyme combination of xylanase, amylase and protease on growth performance and energy utilisation in boiler chickens offered maize-, sorghum- and wheat-based diets and also determine the impact of exogenous enzymes on digestive dynamics of starch and protein in the small intestine and their relativity to broiler performance, a 3 × 2 factorial array of dietary treatments were offered to 288 male Ross 308 chicks from 7 to 27 days post-hatch. Apparent digestibility coefficients of starch, protein and fat in the proximal jejunum, distal jejunum, proximal ileum and distal ileum were determined at Day 27. The digestion rates of starch, protein and energy were predicted by using exponential mathematical models to fit apparent digestibility coefficients with mean retention times in each small intestinal segment. Sorghum-based diets supported the highest weight gain (P < 0.05) and feed intake (P < 0.05) but feed conversion ratios (FCR) were similar across all three grain-based diets (P > 0.10). There were significant interactions between grain type and enzyme supplementation in FCR and the enzyme combination significantly improved FCR in maize-based diets only (P < 0.01). The enzyme combination significantly increased apparent metabolisable energy (AME) in all three grain-based diets (P < 0.05) and increased nitrogen-corrected apparent metabolisable energy (AMEn) in maize- and wheat-based diets (P < 0.05). Wheat-based diets had the lowest N retention (P < 0.01), relative gizzard weight (P < 0.001) and highest gizzard pH (P < 0.05). There were significant grain × enzyme supplementation interactions for starch (P < 0.01) and N (P < 0.05) digestibility coefficients in the four small intestinal segments. Starch digestibility responses to the enzyme combination were most pronounced in wheat-based diets with significant improvement in all segments. The enzyme combination significantly retarded starch digestion rates (P < 0.05) but did not influence protein (N) digestion rates (P > 0.25). In conclusion, feed conversion of sorghum-based diet (1.475) was significantly more efficient than those based on maize (1.518) and wheat (1.532) in non-supplemented diets. The enzyme combination significantly improved energy utilisation (AME) in all three grain-based diets and improved feed conversion efficiency in maize-based diets.